From the viewpoint of environmental preservation, attention is paid to ecofriendly, pollution-free type powder coating that uses no solvents. One of such powder coating methods is an electrostatic fluidized dipping method. In the electrostatic fluidized dipping method, a tank for storing a powder coating material is formed at a lower portion of a substantially closed booth, and air is blown into the storage tank to thereby cause the charged powder coating material to fly up within the booth. Then, in such an atmosphere, an electrically grounded object to be coated is introduced above the storage tank, and the powder coating material is caused to adhere onto the surface of the object to be coated by an electrostatic force.
According to this method, coating is carried out within the booth, and thus powder coating can be performed on the surface of the object to be coated while preventing the splashing and adhesion of the powder coating material onto peripheral equipment, etc., arranged outside the booth.
However, since fluctuation of particle diameter occurs in the powder coating material, finer particles are easily blown up while particles having larger sizes are hardly blown up. Since the particles of the coating material are thus classified, those particles having such a large size so as not to be blown up from the storage tank located in the lower portion of the booth to the object to be coated do not contribute to the formation of a film on the surface of the object to be coated. Therefore, there is a problem inherent in the conventional method that the use efficiency of the coating material was lowered.